The present invention relates to integrated circuit packages for passive infrared sensor.
Passive infrared (PIR) integrated-circuit sensors are integrated-circuit packages, or "chips" as they are called in the technical vernacular, that receive infrared radiation and provide an electrical output signal representing the received infrared radiation. They are used in a wide variety of devices such as infrared motion detection devices. The motion detector devices are commonly used in automatic light switches and security systems to turn on a light or to activate some other form of alarm or warming indicator when a person or other suitably warm object enters a monitored area. These motion detector devices may be used in residential lighting, for example, to illuminate a walkway as a person approaches the front door or to illuminate a driveway as a car approaches. They are also popular as energy saving devices in large office buildings or industrial plants, which may have hundreds of rooms to be illuminated day and night. The motion detection devices can save considerable energy and cost by automatically extinguishing the lights in unoccupied rooms.
Passive infrared motion detector devices function by sensing heat in the form of infra-red radiation emanating from a person or similarly warm object as the person or object enters or moves about in the field of view of the device. An arrangement of mirrors and/or lenses directs the incident infra-red radiation to one or more of the integrated-circuit PIR sensor chips, and when the sensor chip or chips detect an appropriate heat impulse, the motion detector device provides an electrical signal to activate the light or other alarm.
In the many practical applications of PIR motion detectors, it is advantageous to provide wider and wider fields of view. Known PIR sensor chips, however, are limited in the field of view over which they are sensitive. These integrated-circuit sensor packages typically include one or more planar sensing elements which are irradiated through a window on the surface of the IC package. These IC sensor packages are most sensitive to head-on radiation, incident at 90.degree. to the window surface. Their sensitivity drops off the more the incident radiation approaches the sensor from the side, i.e., the more the radiation approaches the sensor at a glancing angle. To achieve a wide field of view, known motion detectors generally require complicated, or costly, optical arrangements for directing the infrared radiation from the outlying reaches of the desired field of view into the significantly narrower angular reach of the sensor sensitivity. Some motion detectors have achieved wider fields of view by compounding a plurality of integrated-circuit sensor packages, each having its own limited field of view, with optical arrangements that bring the incident radiation to the proper sensor at the proper angle to be perceived. In any event motion detectors with wide fields of view have generally involved a tradeoff among increases in cost, complexity, and the physical size of the motion detector unit, and a compromise in performance. For motion detectors approaching a full 360.degree. field of view the tradeoff is all the more stringent.